Storage Solutions

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Deep within the recesses of your computer’s case, a hard drive chugs away with more than just a little effort and precision. While flat-panel monitors, next-generation graphics cards and dual-core CPUs get all the limelight and hog all the glory, the hard drive and other data storage devices do their duty faithfully, keeping safe the gigabytes of data that make up your computer’s programs and your precious data.

The storage of bits and bytes occurs in a wide variety of devices magnetic and optical, random access and linear. Hard drives, for instance, use magnetism to store their goods, writing the data to specially coated, spinning metal platters with magnetic heads that hurry back and forth. Optical devices included CD and DVD readers and burners, which use lasers to read and etch microscopic “pips” on those shiny reflective disks.Random access storage is usually disk-based, the term meaning that any part of the disks can be accessed within milliseconds of a command, so data can be quickly read or written. Linear media aren’t popular as random access media; they include tapes, which have to be fast-forwarded and rewound to locate data.

Most data are stored on a given system’s hard drive, which is considered fixed media storage. The opposite, removable media storage, includes anything that you’d normally detach from or remove from a computer, such as optical disks, floppy diskettes and keychain flash drives. Most computers use a number of different types of storage drives to warehouse data for the long term, to allow new programs and data to be installed, and to back up data or transfer data to other computers.

Hard Drive Technology

Three flavors of hard drives are available for internal fixed disk storage. One is on its way out, one is being ushered in, and one is a steadfast survivor. Respectively, the technologies are known as IDE, Serial ATA (SATA)and SCSI.It no longer really matters what those acronyms stand for; the heart of the matter is what the drives are capable of.

Besides capacity in gigabytes, hard drives are typically categorized by their burst rate, or how fast they can transfer data to the motherboard if all conditions are perfect.You’ll also see seek time (the time it takes in milliseconds to find something requested by a program), spindle rate (the speed, in rotations per minute, at which the hard disk platters spin, which often affects seek time), and cache size (the size of the logic cache on which data are stored to be accessed faster than can be accessed through the read/write heads; the drive caches what it thinks the program will request next, and when it’s correct it’s called a cache hit, and the data are transferred almost instantly). Current consumer-grade drives have burst rates of 133 megabytes per second, 150 MB/s, and 300 MB/s. They seek in less than 9 milliseconds, spin at 7200 or 10,000 RPM, and a typical cache is 2MB or 8MB.

IDE is the old standard, and it’s reached its limits. Using burst technology and wide cables, the industry stretched them from bursting at less than 33 MB/s all the way to near 133 MB/s, but it just can’t go any faster. Thus, bursting technology is called Ultra-ATA, and it was terrific in its time. An Ultra-ATA/133 (with a burst rate of 133 MB/s) is a speedy drive, but it’s the very upper limit of IDE technology. If you purchase a new computer, it’s likely to contain a SATA drive.

SATA uses a thinner cable. It’s a serial technology, meaning it transfers its data sequentially. IDE is a parallel technology, meaning it sends lots of data at once. Original SATA drives burst at 150 MB/s, a solid leap beyond what IDE can do. Newer SATA II drives are capable of 300 MB/s bursts, which is phenomenal.

IDE and SATA use the same command set, meaning that SATA is literally a drop-in replacement for IDE. However, they differ in many ways:

IDE channels can each handle two drives (such as hard drives, optical drives, tape drives, Zip drives, and so on).

A SATA channel is connected directly to one drive, and currently only hard drives are available.

IDE uses a wide cable with 40 or 80 wires, and 40 connector pins.

SATA uses a thin cable with four wires and seven connector pins.

All motherboards support IDE, and newer ones also support SATA. If your motherboard doesn’t support SATA, you can add a PCI SATA card to add one or more SATA hard drives.

SATA is more than capable of all the performance any consumer needs–even for a gamer who demands the speediest and most advanced technology available. There is a third type of hard drive, however, that’s used mostly in servers and the machines of speed-obsessed, hardcore geeks. It’s called SCSI (pronounced “skuzzy”).

SCSI isn’t supported by most motherboards. You need a host adapter to connect a SCSI drive to a system. Quality host adapters and SCSI drives cost considerably more than any IDE or SATA equipment. Current SCSI technology, called Ultra320, bursts at 320 MB/s, just a bit faster than SATA II.

Got all that? If you’re in the market for a hard drive, you first need to find out what your computer supports. Chances are it’s IDE or, if you bought it recently, SATA.

You then need to determine if it contains an available channel or connector for your new drive, unless you’re completely replacing the current drive.

Unless you’re running a server for a corporation with many computers, IDE or SATA will do nicely; they’re easy to work with, price-friendly, and more than fast enough for any consumer application.

RAID stands for Redundant Array of Inexpensive Disks, and it uses two or more hard drives connected to special channels governed by a RAID controller. While RAID can increase performance by striping data across more than one drive, it is mainly used to protect from data loss due to equipment failure. With multiple drives containing the same data, if one drive should fail by seizing up or something, the data are safe on other drives.

There are many RAID “levels,” which contain various RAID technologies. Consumers are likely to encounter RAID 0–which isn’t really RAID, as the data are not redundant–RAID 1, and RAID 0+1. RAID 0 stripes data across two identical drives; with two drives working in unison, multiple data requests can be handled more efficiently, resulting in a mild increase in system performance.

RAID 1 mirrors data from one drive or set of drives onto an identical drive or set, creating protective redundancy. RAID 0+1 requires a minimum of four drives, and combines the striping of RAID 0 with the redundancy of RAID 1 for a performance increase along with data protection. Many current motherboards offer basic RAID options onboard.

Optical Storage

So your computer has a hard drive, which stores data and programs. You need a way to get new applications and games onto that drive, and although more and more products are available for download, you’ll still encounter boxed product containing CD- or DVD-ROM disks. You install such programs via your computer’s optical drive. Not only that, but you can use your optical drive, if it’s a burner, to back up data and to create audio and video disks.

The most basic optical drive is a CD-ROM drive which reads CD-ROMs and music CDs. CD writers, called CD-RW drives, can read CD-ROMs and burn (write) data and music to writeable or rewriteable media.

Then there are DVD-ROM drives, which can read DVD-ROM media and movies, and can also read anything that comes on CD. For several years, many people had two drives: a DVD reader and a CD reader/writer. The industry responded with DVD-ROM/CD-RW combo drives that can read DVD stuff and read and write CD stuff.

Writeable DVDs come in a wealth of standards: DVD+RW, DVD-RW, and DVD-RAM. Thankfully, current drives can read from and write to any of these standards, plus read and write data and music CDs, and pretty much accomplish anything you might want an optical drive to do.

The latest optical drives can read to and write from dual-layer DVD disks, which hold more data than standard DVDs.

Optical drives are typically IDE devices. CDs can hold between 650MB and 700MB of data. Standard DVD+/-RW disks can hold 4.7GB of data. Dual-layer DVDs can cram in up to 8.5GB of data. You can get CD and DVD disks that can only been written once, and then the data or media stored on them are permanent. For considerably more money, you can get rewriteable disks, to which you can write data or burn media many times over.

Other Forms of Storage

Equipped with a hard drive and a pleasing optical drive that does whatever you want it to do, your computer’s basic storage needs are complete. There are other forms of storage, however, aimed mainly at lending convenience to your computing experience.

External hard drives, attached to the computer’s USB 2.0 or FireWire ports, have capacities rivaling those of internal drives, but they can be detached and carried around anywhere. An external hard drive is an excellent option for expanding the storage capacity of a notebook computer or other systems into which you can’t just throw a second internal hard drive.

USB “keychain” drives, which contain flash memory, have limited capacities (most top out around 2GB), but are very handy for backing up critical files or moving data from one computer to another without a network.

Removable media drives, such as floppy drives, are still holding strong. While standard floppy diskettes only hold 1.4MB of data, they’re sometimes required for tasks like flashing a motherboard BIOS or installing drivers during a Windows installation. Alternatives to floppy drives, like Iomega Zip drives, which hold up to 750MB.

Everything I’ve covered deals mainly with consumer-level storage. Turn your attention to enterprise-level storage and you’ll encounter disk and tape arrays, storage area networks (storage devices on their own network, accessed through companies’ various data networks), and dedicated storage machines that hold hundreds of gigabytes, or even terabytes, of data.

As you sit and pound away at your keyboard and click around with your mouse, the computer and its storage devices faithfully handle the important task of keeping your data safe and available. They might not be glamorous, but hard drives and optical drives are just as important as any $600 graphics card.

Joel Durham Jr. is a freelance technology writer and author of “PC Modding for Dummies”(Wiley, 2005).